General synonyms:
* Shelf: A flat, horizontal surface projecting from a wall or other upright structure.
* Sill: A horizontal piece of stone or wood forming the base of a window or door.
* Rim: The edge of a circular or curved surface.
* Brim: The upper edge of a container, typically curved inward.
* Edge: The outer limit of an object or surface.
* Outcropping: A rock formation that protrudes from a cliff face.
More specific synonyms:
* Cornice: A projecting molding along the top of a wall.
* Spar: A projecting rock face, especially in mountainous areas.
* Tread: The horizontal part of a step.
* Landing: A horizontal platform at the top or bottom of a staircase.
Figurative synonyms:
* Platform: A raised area or structure used for a particular purpose.
* Foundation: A base or underlying support.
* Base: The bottom part of something.
To choose the best synonym, consider the specific context in which "ledge" is used. For example, if you're talking about a rock formation, "outcropping" or "spar" would be more appropriate. If you're talking about a shelf, "shelf" or "rim" would be more suitable.